Efficacy Of Detergent Research Articles

Rational Approach to Improve Detergent Efficacy for Membrane Protein Stabilization.

Membrane protein structures are essential for the molecular understanding of diverse cellular processes and drug discovery. Detergents are not only widely used to extract membrane proteins from membranes but also utilized to preserve native protein structures in aqueous solution. However, micelles formed by conventional detergents are suboptimal for membrane protein stabilization, necessitating the development of novel amphiphilic molecules with enhanced protein stabilization efficacy. In this study, we prepared two sets of tandem malonate-derived glucoside (TMG) variants, both of which were designed to increase the alkyl chain density in micelle interiors. The alkyl chain density was modulated either by reducing the spacer length (TMG-Ms) or by introducing an additional alkyl chain between the two alkyl chains of the original TMGs (TMG-Ps). When evaluated with a few membrane proteins including a G protein-coupled receptor, TMG-P10,8 was found to be substantially more efficient at extracting membrane proteins and also effective at preserving protein integrity in the long term compared to the previously described TMG-A13. This result reveals that inserting an additional alkyl chain between the two existing alkyl chains is an effective way to optimize detergent properties for membrane protein study. This new biochemical tool and the design principle described have the potential to facilitate membrane protein structure determination.

Bacillus Swezeyi B2 Strain: A Novel Alkaliphilic Bacterium Producer of Alkaline-, Thermal, Oxidant-, and Surfactant-Stable Protease, Extremely Efficient in Detergency.

Proteolytic enzymes that are currently used to meet industrial demand are usually derived from Bacillus species. They find multiple technical applications, particularly they have been increasingly used as a key bio-additive in detergents. In this study, a novel alkalophilic bacterium was isolated from contaminated soil, exhibiting 1400U/ml proteolytic activity, and identified as Bacillus swezeyi B2. The crude enzyme likely contained a single extracellular protease. This enzyme revealed optimum activity at pH 10 and 70°C and was highly alkaline thermostable (7-12.5) and up to 70°C. The protease activity was completely inhibited by Phenylmethylsulfonyl fluoride (PMSF) suggesting that it belongs to the serine protease group. It was highly stable in the presence of the strong anionic surfactant (SDS) and oxidizing agents (H2O2). The supernatant was lyophilized and showed high storage stability retaining 100% of its original activity after one year of conservation at 4°C. The lyophilized product was evaluated for its detergent efficacy, it revealed excellent compatibility with various laundry detergents keeping its full original activity after incubation for 1h with seven solid and liquid commercial detergents and it effectively removed chocolate stains at low washing temperature (40°C) and low supplementation level (125U/ml). The features of this single alkaline and thermotolerant protease, stable toward surfactants, oxidizing agents, and commercial detergents with stain removal efficacy support its ideal choice for supplementation in detergent formulations.

Decellularized Porcine Pericardium Enhances Autologous Vascularized Matrix as a Prosthesis for Left Ventricular Full-Wall Myocardial Reconstruction

Regenerative grafts for myocardial reconstruction are often mechanically not stable enough to withstand the left ventricle’s high blood pressure. Hence, decellularized pericardium may serve as a stabilizing structure for biological myocardium prostheses. The efficacy of detergent- and enzyme-based protocols to decellularize porcine pericardium was compared. Then, the decellularized pericardium was employed for a primary cover of a transmural left ventricular defect in minipigs (n = 9). This pericardium patch was applied to mitigate the high-pressure load on an autologous stomach tissue, which was utilized as a regenerative tissue prosthesis. Decellularization of the porcine pericardium with deoxycholic acid (DOA)- and enzyme-based protocols (trypsin/EDTA) removed 90% of the original cells (p < 0.001). The trypsin/EDTA protocol significantly altered the matrix architecture compared to the DOA protocol. There were no infections or clinical signs of graft rejection following the transplantation of the decellularized pericardium and the autologous segment of the stomach in the surviving animals (n = 7). A good left ventricular function could be detected via MRI six months following surgery. The biological integration of the graft into the host’s tissue was found histologically. The stabilization of initially fragile grafts with decellularized pericardium facilitates the application of regenerative myocardial prostheses even on the left ventricle.

Efficacy of Newly Emerging Detergents, Laundry Bleach, and Toilet Soap against Bacteria Isolated from Fairly used Clothes, Male/Female Underwear

The aim of this study is to determine the potency of newly emerging detergents, laundry bleach, and toilet soap on bacteria isolates from fairly used clothes and Female Underwear. The current study included sample collection from used clothing and female underwear and compared the efficacy of detergents, toilet soap and laundry bleach (Jik),to reduce the microbial load in the used cloth. Organisms were isolated from the used cloth and female underwear, identified, and microbiologically characterized using the conventional method of microbiology assay. i.e, biochemical test,a compilation of cultural colonial and characteristics. Test Samples were washed using four (4) types of detergents and five (5) types of toilet soap and laundry bleach. The results of the colony-forming unit (CFU) before and after washing with detergent and toilet soap and laundry bleach were recorded, washing with detergents and toilet soap. The results showed that detergents were more effective in reducing bacterial load than toilet soap in all test samples. the addition of laundry bleach (Jik) also shows the effectiveness in reducing bacterial load in fairly used clothes and Female Underwear The antibiotics susceptibility test were determined using disc diffusion and agar well diffusion methods respectively. Eight (8) bacteria were identified include Aerobacter aerogenes (3), Bacillus polymyxa (5), Staphylococcus aureus (2), Veillonella parvula (5), Escherichia freundii (1), Escherichia coli (3), Enterobacter aerogenes (2) and Aerobacter cloacae (1). Bacillus polymyxa, and Veillonella parvula were the most common organism isolated and followed by Escherichia coli from fairly used clothes and Female Underwear. In this study, some of the Gram-positive(+ve) bacteria isolates were sensitive to commonly used antibiotics like Streptomycin, Tarivid, Reflacine Ciprofloxacin, Augmentin, Gentamycin, Ceporex, Nalidixic acid, Septrin, and Amplicin. Gram-negative bacteria isolated were sensitive to Ciprofloxacin and all the isolated organisms were resistant to Ceporex. Gram-positive (-ve) bacteria were sensitive to Streptomycin and were resistant to Rifampicin. To determine the growth dynamics and killing kinetics of the isolated organisms, from fairly used clothes and Female Underwear, an Ultraviolet spectrophotometer were used to determine the wavelength and killing kinetics of isolated organisms from fairly used clothes and Female Underwear. The addition of antibiotics to the isolated organisms at the 48th-hour speed up the death rate of the isolates from fairly used clothe washed with different detergent Laundry Bleach and toilet soaps. It can be deduced that this study validates the efficacy of newly emerging detergents, Laundry bleach, and toilet soap against bacteria isolated from fairly used clothes. It is also recommended to wash fairly used clothes using different methods of soaking the fairly used clothes and female underwear in the Laundry Bleach for some days before finally washing in detergents and ironing before use. This method will drastically reduce and remove bacterial load in the fairly used clothes and female underwear.

Glyco-Steroidal Amphiphiles (GSAs) for Membrane Protein Structural Study.

Integral membrane proteins pose considerable challenges to high resolution structural analysis. Maintaining membrane proteins in their native state during protein isolation is essential for structural study of these bio-macromolecules. Detergents are the most commonly used amphiphilic compounds for stabilizing membrane proteins in solution outside a lipid bilayer. We previously introduced a glyco-diosgenin (GDN) detergent that was shown to be highly effective at stabilizing a wide range of membrane proteins. This steroidal detergent has additionally gained attention due to its compatibility with membrane protein structure study via cryo-EM. However, synthetic inconvenience limits widespread use of GDN in membrane protein study. To improve its synthetic accessibility and to further enhance detergent efficacy for protein stabilization, we designed a new class of glyco-steroid-based detergents using three steroid units: cholestanol, cholesterol and diosgenin. These new detergents were efficiently prepared and showed marked efficacy for protein stabilization in evaluation with a few model membrane proteins including two G protein-coupled receptors. Some new agents were not only superior to a gold standard detergent, DDM (n-dodecyl-β-d-maltoside), but were also more effective than the original GDN at preserving protein integrity long term. These agents represent valuable alternatives to GDN, and are likely to facilitate structural determination of challenging membrane proteins.

Conformationally flexible core-bearing detergents with a hydrophobic or hydrophilic pendant: Effect of pendant polarity on detergent conformation and membrane protein stability

Membrane protein structures provide atomic level insight into essential biochemical processes and facilitate protein structure-based drug design. However, the inherent instability of these bio-macromolecules outside lipid bilayers hampers their structural and functional study. Detergent micelles can be used to solubilize and stabilize these membrane-inserted proteins in aqueous solution, thereby enabling their downstream characterizations. Membrane proteins encapsulated in detergent micelles tend to denature and aggregate over time, highlighting the need for development of new amphiphiles effective for protein solubility and stability. In this work, we present newly-designed maltoside detergents containing a pendant chain attached to a glycerol-decorated tris(hydroxymethyl)methane (THM) core, designated GTMs. One set of the GTMs has a hydrophobic pendant (ethyl chain; E-GTMs), and the other set has a hydrophilic pendant (methoxyethoxylmethyl chain; M-GTMs) placed in the hydrophobic-hydrophilic interfaces. The two sets of GTMs displayed profoundly different behaviors in terms of detergent self-assembly and protein stabilization efficacy. These behaviors mainly arise from the polarity difference between two pendants (ethyl and methoxyethoxylmethyl chains) that results in a large variation in detergent conformation between these sets of GTMs in aqueous media. The resulting high hydrophobic density in the detergent micelle interior is likely responsible for enhanced efficacy of the M-GTMs for protein stabilization compared to the E-GTMs and a gold standard detergent DDM. A representative GTM, M-GTM-O12, was more effective for protein stability than some recently developed detergents including LMNG. This is the first case study investigating the effect of pendant polarity on detergent geometry correlated with detergent efficacy for protein stabilization. Statement of significanceThis study introduces new amphiphiles for use as biochemical tools in membrane protein studies. We identified a few hydrophilic pendant-bearing amphiphiles such as M-GTM-O11 and M-GTM-O12 that show remarkable efficacy for membrane protein solubilization and stabilization compared to a gold standard DDM, the hydrophobic counterparts (E-GTMs) and a significantly optimized detergent LMNG. In addition, detergent results obtained in the current study reveals the effect of detergent pendant polarity on protein solubility and stability. Thus, the current study represents both significant chemical and conceptual advance. The detergent tools and design principle introduced here advance protein science and facilitate structure-based drug design and development.

Diastereomeric Cyclopentane-Based Maltosides (CPMs) as Tools for Membrane Protein Study.

Amphiphilic agents, called detergents, are invaluable tools for studying membrane proteins. However, membrane proteins encapsulated by conventional head-to-tail detergents tend to denature or aggregate, necessitating the development of structurally distinct molecules with improved efficacy. Here, a novel class of diastereomeric detergents with a cyclopentane core unit, designated cyclopentane-based maltosides (CPMs), were prepared and evaluated for their ability to solubilize and stabilize several model membrane proteins. A couple of CPMs displayed enhanced behavior compared with the benchmark conventional detergent, n-dodecyl-β-d-maltoside (DDM), for all the tested membrane proteins including two G-protein-coupled receptors (GPCRs). Furthermore, CPM-C12 was notable for its ability to confer enhanced membrane protein stability compared with the previously developed conformationally rigid NBMs [J. Am. Chem. Soc. 2017, 139, 3072] and LMNG. The effect of the individual CPMs on protein stability varied depending on both the detergent configuration (cis/trans) and alkyl chain length, allowing us draw conclusions on the detergent structure-property-efficacy relationship. Thus, this study not only provides novel detergent tools useful for membrane protein research but also reports on structural features of the detergents critical for detergent efficacy in stabilizing membrane proteins.

English

The emergence and spread of multidrug-resistant microorganisms are threats to public health due to its related increasing rates of morbidity and mortality in the world. Routine disinfection practices do not eliminate many of these resistant species and may contribute to the development in their resistance. Therefore, the current study evaluates the effectiveness of some popular detergents labelled as antibacterial and available at local market. Fifteen different brands of detergents were tested against thirteen American-type culture collection (ATCC) strains; five species related to Gram-positive bacteria, eight species to Gram-negative bacteria and three clinical isolates, (Escherichia coli, Klebsiella pneumonia and Methicillin resistant Staphylococcus aureus (MRSA) by measuring their efficacy by agar well diffusion technique and contact time assay. Dilution levels of detergents exhibited different zones of inhibition against the tested bacterial strains. The initial dilutions of detergents (DAC, SUNOVA, CLOROX, Drummer, GENTO, Dettol with pine, Dettol, Clorox Original, EMLAG and 3 M) showed inhibition zones ranging from 10 mm to >40 mm on Gram positive bacteria. Dettol, Clorox Original, EMLAG and 3 M showed inhibition zones ranging from 11 to 20 mm on limited numbers of Gram-negative bacteria at the first dilutions of detergents. The results showed that, Dettol, Clorox and 3 M were the strongest detergents compared to the other detergents included in this study. A contact-time assay showed a positive relationship between exposure time and efficacy of detergent against the tested bacterial strains.   Key words: Detergents, multidrug-resistant microorganisms, nosocomial infection, Makkah.

A New Method to Evaluate the Antimicrobial Efficacy of Domestic Laundry Detergents

AbstractDuring the last decades, the strive for energy efficiency lead to lower washing temperatures in laundering processes. In this regard, there is a rising need to measure the antimicrobial action of laundry detergents and additives, since chemistry must be considered an important means to compensate for the loss of temperature. Although there is an existing standard method (EN 16616) to evaluate the antimicrobial efficacy of detergents for the medical area, this method does not reflect the domestic situation and neglects important steps, such as the rinse cycles. Hence, we developed an experimental setup, which represents the whole washing process and reflects the domestic situation by using a household‐related setting. The suggested method uses a lab‐scale washing machine, which does not only allow to test products that can be applied throughout the whole laundering process (including the rinse steps) but also proved to be able to show the impact of different parameters (e.g., detergent ingredient or different types of textiles) in a very systematic manner.

Washer disinfector and alkaline detergent efficacy against C. difficile on plastic bedpans

Clostridioides difficile is a major cause of infectious antibiotic resistant diarrhea. C. difficile spores are shed in patient stool, are hearty and difficult to kill. Bedpans are often used by patients with C. difficile infections and require proper handling and cleaning or disposal to prevent the transmission of C. difficile spores and other infectious microorganisms into the environment. Disposable bedpans are often used for convenience, which has consequences from an environmental sustainability perspective. This study evaluates the ability for a washer-disinfector device (WD) to efficaciously clean and disinfect C. difficile spores and Escherichia coli from bedpans for sanitary reuse. A commercially available WD device was evaluated for both efficacy and thermal disinfection against C. difficile spores and Escherichia coli using one disinfection cycle per test. Bedpans were not rinsed or dumped prior to placement in the WD. Bedpans were sampled using swabs. Microorganisms were eluted from the swabs and log-kill was calculated. The average log-kill for C. difficile spores was 3.99 and >7.69 for E. coli. Thermal disinfection results showed an average log kill of 4.31 for C. difficile and >7.23 for E. coli. The WD was efficacious against both C. difficile spores and E. coli when used according to manufacturer's instructions for use, suggesting a viable alternative to disposable bedpan waste management.

The polytetrafluoroethylene (PTFE) channel model of cyclic-buildup biofilm and traditional biofilm: The impact of friction, and detergent on cleaning and subsequent high-level disinfection.

To evaluate the efficacy of detergent and friction on removal of traditional biofilm and cyclic-buildup biofilm (CBB) from polytetrafluoroethylene (PTFE) channels and to evaluate the efficacy of glutaraldehyde to kill residual bacteria after cleaning. PTFE channels were exposed to artificial test soil containing 108 CFU/mL of Pseudomonas aeruginosa and Enterococcus faecalis, followed by full cleaning and high-level disinfection (HLD) for five repeated rounds to establish CBB. For traditional biofilm, the HLD step was omitted. Cleaning with enzymatic and alkaline detergents, bristle brush, and Pull Thru channel cleaner were compared to a water flush only. Carbohydrate, protein, viable count, adenosine triphosphate (ATP) levels were analyzed and atomic force microscopy (AFM) was performed. In the absence of friction, cleaning of traditional biofilm and CBB was not effective compared to the positive control (Dunn-Bonferroni tests; P > .05) regardless of the detergent used. ATP, protein, and carbohydrate analyses were unable to detect traditional biofilm or CBB. The AFM analysis showed that fixation resulted in CBB being smoother and more compact than traditional biofilm. Friction during the cleaning process was a critical parameter regardless of the detergent used for removal of either traditional biofilm or CBB. Glutaraldehyde effectively killed the remaining microorganisms regardless of the cleaning method used.

Self‐Assembly Behavior and Application of Terphenyl‐Cored Trimaltosides for Membrane‐Protein Studies: Impact of Detergent Hydrophobic Group Geometry on Protein Stability

Amphipathic agents are widely used in various fields including biomedical sciences. Micelle-forming detergents are particularly useful for in vitro membrane-protein characterization. As many conventional detergents are limited in their ability to stabilize membrane proteins, it is necessary to develop novel detergents to facilitate membrane-protein research. In the current study, we developed novel trimaltoside detergents with an alkyl pendant-bearing terphenyl unit as a hydrophobic group, designated terphenyl-cored maltosides (TPMs). We found that the geometry of the detergent hydrophobic group substantially impacts detergent self-assembly behavior, as well as detergent efficacy for membrane-protein stabilization. TPM-Vs, with a bent terphenyl group, were superior to the linear counterparts (TPM-Ls) at stabilizing multiple membrane proteins. The favorable protein stabilization efficacy of these bent TPMs is likely associated with a binding mode with membrane proteins distinct from conventional detergents and facial amphiphiles. When compared to n-dodecyl-β-d-maltoside (DDM), most TPMs were superior or comparable to this gold standard detergent at stabilizing membrane proteins. Notably, TPM-L3 was particularly effective at stabilizing the human β2 adrenergic receptor (β2 AR), a G-protein coupled receptor, and its complex with Gs protein. Thus, the current study not only provides novel detergent tools that are useful for membrane-protein study, but also suggests a critical role for detergent hydrophobic group geometry in governing detergent efficacy.

Steroid-Based Amphiphiles for Membrane Protein Study: The Importance of Alkyl Spacers for Protein Stability.

Membrane proteins allow effective communication between cells and organelles and their external environments. Maintaining membrane protein stability in a non-native environment is the major bottleneck to their structural study. Detergents are widely used to extract membrane proteins from the membrane and to keep the extracted protein in a stable state for downstream characterisation. In this study, three sets of steroid-based amphiphiles-glyco-diosgenin analogues (GDNs) and steroid-based pentasaccharides either lacking a linker (SPSs) or containing a linker (SPS-Ls)-have been developed as new chemical tools for membrane protein research. These detergents were tested with three membrane proteins in order to characterise their ability to extract membrane proteins from the membrane and to stabilise membrane proteins long-term. Some of the detergents, particularly the SPS-Ls, displayed favourable behaviour with the tested membrane proteins. This result indicates the potential utility of these detergents as chemical tools for membrane protein structural study and a critical role of the simple alkyl spacer in determining detergent efficacy.

Comparative interaction study of amylase and surfactants for potential detergent formulation

Enzymes have been widely used in modern detergents, however, few studies deal with enzymes dosage as well as its relationship with the other. Enzyme based detergents have been used for remodeling the cleaning efficiency of detergents for many years. Enzyme amylase finds its application in all the industrial processes for the hydrolysis of starch. Amylase is also known for improving detergent efficacy especially at lower temperatures and at lower pH levels. Presence of different surfactant also plays an important role in enhancing the detergent efficacy. So, this paper investigates the physico-chemical properties to obtain the critical micellar concentration (CMC), the thermodynamic parameters (ΔH°m, ΔG°m, ΔS°m) of anionic surfactant sodium dodecyl sulfate (SDS), cationic surfactant cetyl trimethyl ammonium bromide (CTAB) and non-ionic surfactant TWEEN 20 in the presence of an enzyme Aspergillus oryzae originated α-amylase at varying temperatures for formulating a possible better combination of surfactant and amylase for making an eco-friendly detergent. Further surface tension studies, the kinetic studies (Km and Vmax values) have been carried out. Then the degradation studies have been performed to calculate the biological oxygen demand (BOD) to conduct a comparative analysis which would be helpful in potential detergent formulation and in analyzing their environmental impact as minimal the BOD, maximal the degradation of formulated detergent on dispose off.

Vitamin E-based glycoside amphiphiles for membrane protein structural studies.

Membrane proteins play critical roles in a variety of cellular processes. For a detailed molecular level understanding of their biological functions and roles in disease, it is necessary to extract them from the native membranes. While the amphipathic nature of these bio-macromolecules presents technical challenges, amphiphilic assistants such as detergents serve as useful tools for membrane protein structural and functional studies. Conventional detergents are limited in their ability to maintain the structural integrity of membrane proteins and thus it is essential to develop novel agents with enhanced properties. Here, we designed and characterized a novel class of amphiphiles with vitamin E (i.e., α-tocopherol) as the hydrophobic tail group and saccharide units as the hydrophilic head group. Designated vitamin E-based glycosides (VEGs), these agents were evaluated for their ability to solubilize and stabilize a set of membrane proteins. VEG representatives not only conferred markedly enhanced stability to a diverse range of membrane proteins compared to conventional detergents, but VEG-3 also showed notable efficacy toward stabilization and visualization of a membrane protein complex. In addition to hydrophile-lipophile balance (HLB) of detergent molecules, the chain length and molecular geometry of the detergent hydrophobic group seem key factors in determining detergent efficacy for membrane protein (complex) stability.

Butane-1,2,3,4-tetraol-based amphiphilic stereoisomers for membrane protein study: importance of chirality in the linker region.

Amphiphile selection is a crucial step in membrane protein structural and functional study. As conventional detergents have limited scope and utility, novel agents with enhanced efficacy need to be developed. Although a large number of novel agents have been reported, so far there has been no systematically designed comparative study of the protein stabilization efficacy of stereo-isomeric amphiphiles. Here we designed and prepared a novel class of stereo-isomeric amphiphiles, designated butane-1,2,3,4-tetraol-based maltosides (BTMs). These stereoisomers showed markedly different behaviour for most of the targeted membrane proteins depending on the chirality of the linker region. These findings indicate an important role for detergent stereochemistry in membrane protein stabilization. In addition, we generally observed enhanced detergent efficacy with increasing alkyl chain length, reinforcing the importance of the balance between hydrophobicity and hydrophilicity in detergent design. The stereo-isomeric difference in detergent efficacy observed provides an important design principle for the development of novel amphiphiles for membrane protein manipulation.

Dendronic trimaltoside amphiphiles (DTMs) for membrane protein study.

The critical contribution of membrane proteins in normal cellular function makes their detailed structure and functional analysis essential. Detergents, amphipathic agents with the ability to maintain membrane proteins in a soluble state in aqueous solution, have key roles in membrane protein manipulation. Structural and functional stability is a prerequisite for biophysical characterization. However, many conventional detergents are limited in their ability to stabilize membrane proteins, making development of novel detergents for membrane protein manipulation an important research area. The architecture of a detergent hydrophobic group, that directly interacts with the hydrophobic segment of membrane proteins, is a key factor in dictating their efficacy for both membrane protein solubilization and stabilization. In the current study, we developed two sets of maltoside-based detergents with four alkyl chains by introducing dendronic hydrophobic groups connected to a trimaltoside head group, designated dendronic trimaltosides (DTMs). Representative DTMs conferred enhanced stabilization to multiple membrane proteins compared to the benchmark conventional detergent, DDM. One DTM (i.e., DTM-A6) clearly outperformed DDM in stabilizing human β2 adrenergic receptor (β2AR) and its complex with Gs protein. A further evaluation of this DTM led to a clear visualization of β2AR-Gs complex via electron microscopic analysis. Thus, the current study not only provides novel detergent tools useful for membrane protein study, but also suggests that the dendronic architecture has a role in governing detergent efficacy for membrane protein stabilization.

Mesitylene‐Cored Glucoside Amphiphiles (MGAs) for Membrane Protein Studies: Importance of Alkyl Chain Density in Detergent Efficacy

Detergents serve as useful tools for membrane protein structural and functional studies. Their amphipathic nature allows detergents to associate with the hydrophobic regions of membrane proteins whilst maintaining the proteins in aqueous solution. However, widely used conventional detergents are limited in their ability to maintain the structural integrity of membrane proteins and thus there are major efforts underway to develop novel agents with improved properties. We prepared mesitylene-cored glucoside amphiphiles (MGAs) with three alkyl chains and compared these agents with previously developed xylene-linked maltoside agents (XMAs) with two alkyl chains and a conventional detergent (DDM). When these agents were evaluated for four membrane proteins including a G protein-coupled receptor (GPCR), some agents such as MGA-C13 and MGA-C14 resulted in markedly enhanced stability of membrane proteins compared to both DDM and the XMAs. This favourable behaviour is due likely to the increased hydrophobic density provided by the extra alkyl chain. Thus, this study not only describes new glucoside agents with potential for membrane protein research, but also introduces a new detergent design principle for future development.

Isomeric Detergent Comparison for Membrane Protein Stability: Importance of Inter-Alkyl-Chain Distance and Alkyl Chain Length.

Membrane proteins encapsulated by detergent micelles are widely used for structural study. Because of their amphipathic property, detergents have the ability to maintain protein solubility and stability in an aqueous medium. However, conventional detergents have serious limitations in their scope and utility, particularly for eukaryotic membrane proteins and membrane protein complexes. Thus, a number of new agents have been devised; some have made significant contributions to membrane protein structural studies. However, few detergent design principles are available. In this study, we prepared meta and ortho isomers of the previously reported para-substituted xylene-linked maltoside amphiphiles (XMAs), along with alkyl chain-length variation. The isomeric XMAs were assessed with three membrane proteins, and the meta isomer with a C12 alkyl chain was most effective at maintaining solubility/stability of the membrane proteins. We propose that interplay between the hydrophile-lipophile balance (HLB) and alkyl chain length is of central importance for high detergent efficacy. In addition, differences in inter-alkyl-chain distance between the isomers influence the ability of the detergents to stabilise membrane proteins.

A new dry-surface biofilm model: An essential tool for efficacy testing of hospital surface decontamination procedures

The environment has been shown to be a source of pathogens causing infections in hospitalised patients. Incorporation of pathogens into biofilms, contaminating dry hospital surfaces, prolongs their survival and renders them tolerant to normal hospital cleaning and disinfection procedures. Currently there is no standard method for testing efficacy of detergents and disinfectants against biofilm formed on dry surfaces. Aim: The aim of this study was to develop a reproducible method of producing Staphylococcus aureus biofilm with properties similar to those of biofilm obtained from dry hospital clinical surfaces, for use in efficacy testing of decontamination products. The properties (composition, architecture) of model biofilm and biofilm obtained from clinical dry surfaces within an intensive care unit were compared. MethodsThe CDC Biofilm Reactor was adapted to create a dry surface biofilm model. S. aureus ATCC 25923 was grown on polycarbonate coupons. Alternating cycles of dehydration and hydration in tryptone soy broth (TSB) were performed over 12days. Number of biofilm bacteria attached to individual coupons was determined by plate culture and the coefficient of variation (CV%) calculated. The DNA, glycoconjugates and protein content of the biofilm were determined by analysing biofilm stained with SYTO 60, Alexa-488-labelled Aleuria aurantia lectin and SyproOrange respectively using Image J and Imaris software. Biofilm architecture was analysed using live/dead staining and confocal microscopy (CM) and scanning electron microscopy (SEM). Model biofilm was compared to naturally formed biofilm containing S. aureus on dry clinical surfaces. ResultsThe CDC Biofilm reactor reproducibly formed a multi-layered, biofilm containing about 107CFU/coupon embedded in thick extracellular polymeric substances. Within run CV was 9.5% and the between run CV was 10.1%. Protein was the principal component of both the in vitro model biofilm and the biofilms found on clinical surfaces. Continued dehydration and ageing of the model biofilm for 30days increased the % of protein, marginally decreased gylcoconjugate % but reduced extracellular DNA by 2/3. The surface of both model and clinical biofilms was rough reflecting the heterogeneous nature of biofilm formation. The average maximum thickness was 30.74±2.1μm for the in vitro biofilm model and between 24 and 47μm for the clinical biofilms examined. ConclusionThe laboratory developed biofilm was similar to clinical biofilms in architecture and composition. We propose that this method is suitable for evaluating the efficacy of surface cleaners and disinfectants in removing biofilm formed on dry clinical surfaces as both within run and between run variation was low, and the required equipment is easy to use, cheap and readily available.